Each of the six major powers in the 40k galaxy(Barring the Tyranids, since they're mindless animals) are given one of the Infinity Gems from the 616 Marvel Universe by act of God. For this scenario, the gems work despite this not being their home universe.
The Imperium of Man is given the Power Gem. The Eldar are given the Time Gem. The Dark Eldar are given the Mind Gem. The Necrons are given the Soul Gem. The Orks are given the Reality Gem. The Tau are given the Space Gem.
Which faction best makes use of their new powers? Does this event shift the tide a bit and break the 10,000 year galactic stalemate?